MVC架构中控制器与仓库层的职责划分：为何应避免直接调用仓库层

// 概念性代码，非特定框架
class UserController
{
    private UserRepository $userRepository;

    public function __construct(UserRepository $userRepository)
    {
        $this->userRepository = $userRepository;
    }

    public function registerUser(array $requestData)
    {
        // 业务逻辑和数据持久化逻辑混杂在控制器中
        if (empty($requestData['email']) || !filter_var($requestData['email'], FILTER_VALIDATE_EMAIL)) {
            // 处理错误...
            return $this->renderErrorView('Invalid email.');
        }

        $user = new User();
        $user->setName($requestData['name']);
        $user->setEmail($requestData['email']);
        $user->setPassword(password_hash($requestData['password'], PASSWORD_DEFAULT));

        $this->userRepository->save($user); // 直接调用仓库

        // 可能还有发送欢迎邮件等逻辑...

        return $this->redirect('/dashboard');
    }
}

// 概念性代码，非特定框架

// 1. 控制器层
class UserController
{
    private UserService $userService;

    public function __construct(UserService $userService)
    {
        $this->userService = $userService;
    }

    public function registerUser(array $requestData)
    {
        try {
            // 控制器只负责接收输入并委托给服务层
            $this->userService->registerNewUser(
                $requestData['name'],
                $requestData['email'],
                $requestData['password']
            );
            return $this->redirect('/dashboard');
        } catch (InvalidArgumentException $e) {
            // 处理业务逻辑验证失败
            return $this->renderErrorView($e->getMessage());
        } catch (Exception $e) {
            // 处理其他异常
            return $this->renderErrorView('An unexpected error occurred.');
        }
    }
}

// 2. 服务层
class UserService
{
    private UserRepository $userRepository;
    // 可能还有其他依赖，如MailerService等

    public function __construct(UserRepository $userRepository /*, MailerService $mailerService */)
    {
        $this->userRepository = $userRepository;
        // $this->mailerService = $mailerService;
    }

    public function registerNewUser(string $name, string $email, string $password): User
    {
        // 所有的业务逻辑都在服务层处理
        if (empty($email) || !filter_var($email, FILTER_VALIDATE_EMAIL)) {
            throw new InvalidArgumentException("Invalid email format.");
        }
        if ($this->userRepository->findByEmail($email)) {
            throw new InvalidArgumentException("Email already registered.");
        }

        $user = new User();
        $user->setName($name);
        $user->setEmail($email);
        $user->setPassword(password_hash($password, PASSWORD_DEFAULT));

        $this->userRepository->save($user); // 服务层调用仓库

        // $this->mailerService->sendWelcomeEmail($user); // 其他业务逻辑

        return $user;
    }
}

// 3. 仓库层
class UserRepository
{
    public function save(User $user): void
    {
        // 仅处理数据持久化逻辑
        // 例如：使用ORM或SQL语句将User对象保存到数据库
        echo "Saving user to database: " . $user->getEmail() . "\n";
    }

    public function findByEmail(string $email): ?User
    {
        // 从数据库查找用户
        echo "Finding user by email: " . $email . "\n";
        // 模拟查找结果
        if ($email === 'existing@example.com') {
            $user = new User();
            $user->setEmail($email);
            $user->setName('Existing User');
            return $user;
        }
        return null;
    }
}

// 4. 领域模型 (User)
class User
{
    private string $name;
    private string $email;
    private string $passwordHash;

    // Getters and Setters...
    public function setName(string $name): void { $this->name = $name; }
    public function getName(): string { return $this->name; }
    public function setEmail(string $email): void { $this->email = $email; }
    public function getEmail(): string { return $this->email; }
    public function setPassword(string $passwordHash): void { $this->passwordHash = $passwordHash; }
}